1. Field of the Invention
This invention relates to an electric motor type injection apparatus for a vertical molding machine constituted by installing an injection apparatus longitudinally on a movable platen installed on a mold base provided on a machine bed in a manner to lift and lower freely while a heating cylinder comprised by the injection apparatus is directed downwardly.
2. Background Art
In a general electric motor type injection apparatus, an electric motor is utilized as a driving source for touching a nozzle, metering, injecting and so on. There is no problem on installing especially even though three electric motors being utilized as driving sources, because an installing space of the electric motor can be kept sufficiently in a transverse type molding machine. However the square measure of the machine bed in the case of a vertical molding machine is limited, and moreover, it has been desired from the viewpoint of stability that three electric motors are mounted on the injection apparatus in compact so that the injection apparatus can be accommodated in well-balanced conditions within the square measure of the machine bed.
Moreover, in the case of the transverse molding machine, the entire apparatus is arranged and supported on the machine bed long in the transverse direction and the direction of the movement also is in the horizontal direction, whereby movability due to self-weight of an injection driving device and an injection screw in the heating cylinder can be neglected. However, on the other hand, in the case of the vertical molding machine, the entire apparatus is arranged and extended in the longitudinal direction on the machine bed, whereby the injection driving device supported in a manner to lift and lower freely by a shaft and the injection screw or the like installed in a downward direction in the heating cylinder have tendency to move downwardly due to self-weight. A stopping position of the injection screw is made uncertain by this downward movement due to the self-weight and have tendency to overrun at a metering completion position, whereby an over packing of material tends to be caused. Moreover, when a nozzle of the injection apparatus is touched to a mold, this results in the cause of generation of the improper nozzle touch force due to the load, which the force is in excess of a setting and results in a factor of damage of the nozzle tip.
In a prior vertical molding machine utilized fluid pressure such as hydraulic pressure or air as a driving source, although the downward movement due to self-weight of an injection driving device and an injection screw can be prevented readily using the pressure as resistance, in the case of utilizing an electric motor, a solution by such prior means can not be expected, so that a new preventive measures by mechanical means has been required. As a result, in the electric motor type machine, the constitution cannot but become sophisticated inevitably compared with the prior means driven by hydraulic pressure or air, whereby this also results in increasing of a manufacturing cost.
The injection molds in the vertical molding machine are mounted on the mold base on the machine bed and on an opposite face of the movable platen installed in a manner to lift and lower freely to the mold base, said movable platen being fixed on upper ends of shafts for clamping which also serve as tie bars installed through the four corners of the mold base in a manner to move upwardly and downwardly freely, in the splitted conditions without regard to a driving source utilized therein, and a gate is provided on the central portion of the split mold on the movable platen.
The injection apparatus is centered and installed so that the nozzle of the heating cylinder tip can contact with this gate through the movable platen, and a mounting position of the injection mold also is set so that the gate can be positioned in the nozzle center. However, at exchange of the mold in the factory, the injection mold can not be set in a proper position, and therefore, the gate position is deviated slightly, whereby the normal nozzle touch can not be performed. This deviation results in the cause of damage of the nozzle tip and the gate and results in the cause of a short shot of the injection.
Hitherto, correction of the gate position after exchange of the mold is not performed, and in almost cases, the reset should be performed after detaching the mold. Because the reset of the mold should be performed by detaching not only the mold on the movable platen but also that on the mold base, the reset of the molds is troublesome and results in the molding loss, whereby in many cases, the mold is used without the reset when molding is not interfered because of the slight deviation. Therefore, in the vertical molding machine, the constitution that entering can be performed readily without the reset has been expected.